Enclosed electric arc lamp



5.49% ttorney Sept. 21, 1937.

E. LEMMERS ENCLOSED ELECTRIC ARC LAMP Filed Feb. 26, 1935 Inventor Eugene Lemmers, b 77 9 His Patented 21, 1937 l um'rsn STATES PATENT OFFICE 2.09am apcnosan usc'rmc sac mm Eugene Lemmers, Cleveland, Ohio, asaignor to General Electric Company, a corporation of New York Application February 26, 1935, Serial No. 8,286

. 10 Claims.

will operate eiliciently without the usual enclos ing vacuum Jacket.

An advantage of my lamp is that, because of the operation of the lamp at temperatures rather close to the softening point of theglass used for the envelope which in turn permits the attain-- ment of the desired high vapor pressures. .In lamps having envelopes of conventional shapes, the temperature differential in difi'erent parts of the envelope is so great that when the hot portion is kept safely below the softening point of the glass envelope, the comparatively cooler portion is at too low a temperature to provide the desired high pressure because of the condensation there of the vaporizable metal.

According to my invention the envelope of the lamp is so shaped and the electrodes are mounted in such a manner that the temperature of the bulb during operation is as nearly uniform as possible, while the shape of the envelope is reasonably practical. The said envelope is of larger diameter at the top than at the bottom, the midportion of said envelope preferably increasing in diameter substantially uniformly from the bottom to the top. The said envelope is preferably somewhat oval-shaped. The electrodes are 'disposed in the vertical axis of said envelope so that the positive column path therebetween is in the said vertical axis, the upper electrode being preferably disposed adiacent the largest diameter of said envelope.

Further features and advantages of my inventlon will appear from the following description of species thereof and from the drawing.

The drawing is a vertical elevation of a high pressure'metal vapor (mercury) 'arc lamp constructed in accordance with my invention.

Referring to the drawing, the lamp comprises a glass envelope or bulb I containing a readily ionizable gas, such'as argon, and a vaporizable metal, preferably a globule of mercury ii. A

the comparatively uniform temperature throughout the envelope at operation, it makes possible tween the electrodes.

pair of electrodes i2, II are disposed in the vertical and longitudinalaxis of the envelope ill. The said electrodes may consist of blocks of tungsten impregnated with an electron emissive material, such as barium or strontium oxide or a 5 mixture of such materials. The upper electrode I2 is mounted on a lead wire it, preferably of tungsten, which extends through an axial hole in said electrode. An angular piece of wire I,

preferably a molybdenum wire, is spot welded to the said lead ll and electrode ii to secure the electrode on the lead. The lower electrode II is similarly mounted on a lead wire it and secured by an angular wire II.

A lamp of the particular proportions illustrated l5 in the drawing has been constructed and operated successfully in a 400 watt capacity size. operating at 70 volts and 6.35 amperes. The envelope ill in this case was filled with argon gas at a pressure of 8 mm. and contained .033 cc.

of mercury. As shown, the upper electrode i2 is substantially at the center of curvature of the spherical upper end of the envelope I I, that is, it is adJacent the largest diameter of said envelope. The lower electrode II in this particular portion which increases in diameter substantially uniformly from the lower to the upper end ber The active or arc-sustaining end or surface it of the upper electrode i2 is approximately three times as far from the upper end is of the envelope it as the active end or surface 20 of the lower electrode I8 is from the lower end 2i of said envelope. The distance from the said surface or end I! of electrode i! to the side wall of the envelope Ill opposite thereto is approximately fifty per cent greater 40 than the distance from the surface or end ll of electrode ii to the side wall opposite thereto, that is, the diameter of the envelope l0 adjacent the end iii of electrode I2 is approximately fifty per cent greater than the diameter of said envelope adjacent the end 20 of electrode it.

During operation of a lamp of the proportions described above in a surrounding globe 22, the

temperature of the envelope at' various points was measured and the results were approximately C.,that is, the manimumtemperature of the envelope was less than twenty per cent greater than the minimum temperature. The operat-- ing pressure of the lamp was approximately two atmospheres. It is important in a lamp operating at a pressure in excess of about one atmosphere that the temperature is either the same at all points between the electrodes or that it increases uniformly from the lower to the upper electrode, that is, there must not be a dip in the temperature gradient between the electrodes because the arc would in that case bow out toward the cooler region. When a lamp is made with a plain cylindrical envelope large enough in diameter so that the top is not overheated, the temperature at the bottom is so much lower that the desired mercury pressure cannot be reached due to condensation of the mercury at the bottom.

It will be understood by those skilled in the art that the actual ratios of small bottom diameter to large top diameter of the envelope will vary with changes in arc length, operating pressure, electrode size and shape, total watts, etc. For a lamp operating in the open, that is, without the enclosing globe 22, the bottom diameter is preferably smaller than that of the envelope illustrated in the drawing, more nearly resembling a top" than an oval, because of the cooling efiect of the air passing upward. along said envelope.

The electrodes in the lamp may also be of the indirectly heated or directly heated type. However, they are solid electrodes as distinguished from electrodes of metallic liquid such as mercury.

What I claim as new and desire to secure by Letters Patent of the United States is:

'1. A high pressure metal vapor arc lamp adapted to have its longitudinal axis vertically disposed and comprising an envelope containing a quantity of vaporizable metal, upper and lower electrodes in said envelope disposed in said longitudinal axis, the upper electrode being located at a substantially greater distance from the top of said envelope than the lower electrode is from the bottom of said envelope, the diameter of said envelope adjacent said upper electrode being greater than the diameter of said envelope adjacent said lower electrode, and the portion of said envelope between said electrodes increasing substantially uniformly in diameter from the bottom to the top.

2. A high pressure metal vapor arc lamp adapted. to have its longitudinal axis vertically disposed and comprising an envelope cont a quantity of vaporizablemetal, upper and lower electrodes in said envelope disposed in said longitudinal axis, the distance from the arc smaining surface of the upper electrode to the upper end of said envelope being at least twice the distance from the arc sustaining surface of the lower electrode to the lower end of said envelope, the diameter of said envelope adjacent said upper electrode being greater than the diameter of said envelope adjacent said lower electrode, and the portion of said envelope between said electrodes increasing substantially uniformly in diameter from the bottom to the top.

3. A high pressure metal vapor arc lamp adapted to have its longitudinal axis vertically disposed and comprising an envelope containing a quantity of vaporizable metal, upper and lower electrodes in said envelope disposed in said longi the distance from the arc sustaining surface of the lower electrode to the lower end of said envelope, the diameter of said envelope adjacent said upper electrode being greater than the diameter of said envelope adjacent said lower electrode, and the portion of said envelope between said electrodes increasing substantially uniformly in diameter from the bottom to the top.

4. A high pressure metal vapor arc lamp adapted to have its longitudinal axis vertically disposed and comprising an envelope containing a quantity of vaporizable metal, upper and lower electrodes in said envelope disposed in said longitudinal axis, the distance from the arc sustaining surface of the upper electrode to the upper end of said envelope being at least twice the distance from the arc sustaining surface of the lower electrode to the lower end of said envelope, the diame'terof said envelope adjacent said arc sustaining surface of said upper electrode being at least twenty-five per cent greater than the diameter of said envelope adjacent said are sustaining surface of said lower electrode, and the portion of said envelope between said electrodes increasing substantially uniformly in diameter from the bottom to the top.

5. A high pressure metal vapor arc lamp adapted to have its longitudinal axis vertically disposed and comprising an envelope containing a quantity of vaporizable metal, upper and lower electrodes in said envelope disposed in said longitudinal axis, the distance from the arc sustaining surface of the upper electrode to the upper end of said envelope being at least twice the distance from the arc sustaining surface of the lower elec-= trade to the lower end of said envelope, the diameter of said envelope adjacent said are sustain ing surface of said upper electrode being approximately fifty per cent greater than the diameter of said envelope adjacent said are sustaining sur-= face of said lower electrode, and the portion of said envelope between said electrodes increasing substantially uniformly in diameter from the bottom to the top.

6. A high pressure metal vapor arc.lamp comprising a substantially oval-shaped envelope and adapted to have its longitudinal axis vertically disposed with the larger end of said envelope uppermost, said envelope containing a quantity of vaporizable metal, upper, and lower electrodes in said envelope disposed in said longitudinal axis, the upper electrode being disposed substantially adjacent the largest diameter of said envelope and the lower electrode being disposed substan= tially adjacent the lower end of said envelope.

7. A high pressure metal vapor arc lamp comprising a substantially oval-shaped envelope and adapted to have its longitudinal axis vertically disposed with the larger end of said envelope uppermost, said envelope containing a quantity of vaporizable metal, the upper and lower end portions of said envelope being substantially spherical, upper and lower electrodes in said envelope disposed in said vertical axis, the upper electrode being disposed substantially at the center of curvature of the upper end portion of said envelope and the lower electrode being disposed below the center of curvature of the lower end portion of said envelope.

8. A high pressure metal vapor are lamp adapted to be mounted with its longitudinal axis vertically disposed and to operate at a pressure in excess of one atmosphere and comprising a vitreous envelope containing a quantity of readily vaporizable metal, upper and lower solid else rodes in said envelope. in said longitudinal axis, the upper electrode being located at a substantiallygreater distance from the top oi said envelope than the lower electrode is from the bottom of said envelop and the diameter of said envelope adjacent said upper electrode being substantially greater than the diameter of said envelope adjacent said lower electrode.

9. A high pressure metal vapor arc lamp adapted to be mounted with its longitudinal axis verticaliy disposed and to operate at a pressure in excess of one atmosphere and comprising a vitreous envelope containing a quantity oi readily vaporizable metal, and upper and lower solid electrodes disposed in said longitudinal axis. said envelope being of substantially uniformly increasing diameter i'rom a point adjacent said lower electrode to a point adiaccnt said upper electrode so that the temperature gradient along 20 the wall or said envelope between said electrodes during operation or the lamp is substantially uniform.

10. A high pressure metal vapor arc lamp adapted to be mounted with its longitudinal axis vertically disposed and to operate at a pressure in excess of one atmosphere and comprising a vitreous envelope containing a quantity of readily vaporizable metal, and upper and lower solid electrodes disposed in said longitudinal axis, the diameter of said envelope opposite the upper electrode being greater than the diameter of said envelope opposite the lower electrode, and said envelope between said electrodes being of substantially uniformly increasing diameter from said lower electrode to said upper electrode so that the maximum temperature therein during operation of the lamp is not more than approximately twenty per cent greater than the minimum temperature.

EUGENE LEMMERS. 20 

